President of Croatia Ivo Josipovic said during the signing ceremony that this was an "historic event" for his country.

He recalled that recent Balkan history has been one of war and confrontation.

"Therefore, we can congratulate ourselves,” he said. “The success of Croatia is a European success story and of a policy of peace which is the strongest foundation for a united Europe," Josipovic stressed.

Head of European Commission Jose Manuel Barroso said that the accession treaty is a unique moment for the EU and for Croatia.

"The success we celebrate today is the success of the Croatian nation," he said.

Barroso congratulated the Croatian nation's commitment to Europe. According to Barroso, Croatia has demonstrated that it is ready to meet very difficult conditions necessary for accession to the EU, "fully on 1 July 2013".

In the meantime, Croatia will become more active as an observer at EU meetings and summits.

Croatia is signing into an EU deep in crisis, however, as leaders try to come to agreement on measures to fight the eurozone crisis.

According to the head of the European Commission, the economic crisis should not change the drive for enlargement of the bloc.

EU leaders are also discussing today Serbia's application to join the union.

European Council President Herman Van Rompuy said the EU remained committed to welcoming Balkan states despite the finance crisis.

"The achievement of Croatia proves to all in the region that through hard work, persistence, political courage and determination, EU membership is within reach," Van Rompuy said.

Belgrade will probably be offered a place in the bloc at a summit in March next year.

Poland's prime minister, Donald Tusk, has hailed the conclusion of the Croatian agreement as a major success of the Polish six-month EU presidency, which ends on 31 December. (pg)